Zoos have sought improved barriers for containment of zoo animals with less visually-obtrusive means. The demand for less visible barriers has led to development of a number of different containment strategies. The ultimate goal of an invisible barrier has remained largely unfulfilled for zoo administrators and the general public. Some efforts have been made to achieve this goal by zoo designers working in concert with product manufacturers.
Barriers fall into one or more of the following categories: see-through fencing, including meshes of a variety of materials and descriptions, tension wire and electrified wire; barriers of transparent glass; wet and dry moats; and walls made of simulated rock. Each containment approach has advantages and is useful in certain applications, but there is still plenty of room for improvement, consequently, designers and manufacturers continue to seek new ways to satisfy the demand for better barriers.
Since fencing is usually cheaper than moats, windows, or walls, a major focus has been to develop stronger and less visible cable meshes. In addition, fencing may allow visitors better access and visibility to animals and exhibits. Moats and other such enclosure generally place the viewer at a great distance from the animal or exhibit. Cables made of metal offer many advantages as a fencing material, (i.e., relatively low cost, strength, flexibility, durability, availability, and the like).
The demand for cable netting has led to development of a number of different products. Consequentially, a number of different cable products have been introduced to the markets in recent years. Despite the variety of products now available, there is still a substantial need for improvement.
Cable meshes may be produced by laying out separate cables and joining them to each other in various ways. The challenge here is to join the cables at regular points of intersection in a cost-effective, aesthetic, and dependable manner.
One prior-art netting is comprised of 1/16" or 3/32" stainless steel cables which are joined at regular intervals with cylindrical metal fasteners (e.g., crimp "barrels" or the like) which are threaded over the cables and crimped. Such a netting forms diamond-shaped openings when stretched. Such a prior-art netting may be marketed by Kettner & Associates, Inc. of Mequon, Wis. This prior-art mesh is considered quite effective for containment of mammals, such as leopards and baboons. The crimped connectors are, however, noticeably visible, and the cables are generally thicker than desirable for aviaries and other light-duty enclosures. The crimped meshes are also expensive to produce because the fasteners are threaded over the cables and crimped by hand.
Double tucked cable mesh is another prior-art cable mesh. It is available through Carlos' Designs of Las Vegas, Nev., as well as other mesh manufacturers. It is hand-manufactured so that the individual cables zig-zag back and forth to join alternatively, in a knotless connection, to the adjacent cable on either side. Due to the process of spreading one cable apart so the other can be threaded through the opening, this method requires relatively thick cables to permit separation of the strands.
Single-tucked and hog ringed cable mesh is another prior-art cable mesh. It is produced by International Cordage, Inc. It advantageously employs hog-rings at cable intersections for faster production. Unfortunately, the connections tend to slide, and the cables are also thick. It is relatively labor intensive to produce.
Hog-ringed cable mesh is a less expensive alternative prior-art cable mesh. The cables are advantageously connected without the involvement of threading of wires. Although this mesh is adequate to contain animals that do not place excessive force on the joints, if sufficient tension is placed on any connection, then the cables may slip through the hog rings, forming an opening through which an animal may pass.
Cast-metal connected cable meshes are manufactured in Germany by Pfeifer Nets. The wires are bonded at each intersection with a small cast-metal sphere, so that the sphere rigidly encases the cables. Unlike the connections on hog-ring meshes, these cast-in-place connectors do not slip. They are however, expensive to procure, very visible, and are not practical for use with fine-gauge cables.
Turning now to non-cable meshes, welded wire fabrics are available in very fine gauges. They are useful for containing birds and smaller mammals. However, the quality of the welds tends to be inconsistent, and fatigued wires may break upon repeated flexing.
A mesh known as, Phantom Mesh.TM., is available through A thru Z Consulting and Distributing, Inc. It is appropriate as a low-cost and less-visible containment barrier. It is not a cable mesh. Its design is like that of a chain link, although lighter-gauge wires are used. Although the curved and spiraled contours of the wires reduce visual reflectivity, the wires are however relatively thick and closely spaced, and tend to be noticeably visible.
Another mesh called, Zoomesh.TM., is machine-knitted using a fine wire to form loosely interlocking rows. It is suitable for containing smaller birds and mammals. However, due to lack of wire bonding, the knitting can be snagged. Its fine meshing is difficult to frame, yet noticeably visible to the eyes.
Poultry netting, or a chicken wire, is cheap and offers reasonable visibility, but it is weak and susceptible to breaks when considered for permanent animal housing.
Non-metallic meshes and nets are suitable for some aviary construction. However, non-metallic meshes and nets have been known to be susceptible to chewing by mammals, particularly rodents that may be preying after the feed grain. Similarly, birds are often at risk to predators when housed in aviaries constructed of synthetic materials, because predators have been known to tear and chew through non-metallic meshes and nets.
Most fishnets are non-metallic nets. They are machine tied in large quantities. The prior art net-making machines are generally intricate, expensive, and made for volume production. They are specific to handling of pliable cords for fishnets, and are not known in the industry to be readily adaptable to handling metallic cables, which are not as pliable as the cords for fishnets.
One example of a non-metallic netting is a hand-tied fishnet. This traditional hand-tying technique involves the use of an elongated netting needle. The netting needles are generally narrow. A reasonably large quantity of cord is wrapped around a netting needle. The netting is created by forming a long row of loops, to which is tied a second row of loops, and then a third, etc. The netting needles are narrow because an entire supply of cord must pass through the loop of previously tied mesh to which the new knot is being tied.
This technique of tying a net is ill-suited for modern-day purposes. The process of passing the entire supply of cord on a needle through each loop must be done by hand. Also, the amount of the available cord is limited by the size of the mesh through which the needle passes. These limitations necessitate frequent splicing of cords to produce nets of large size.
The aforementioned prior-art meshes and nets do not satisfactorily meet certain barrier use requirements where strength, see-through visibility, mesh integrity, and ease of production are all high selection criteria.